How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Matt Your Own Question
Matt, Engineer
Category: Australia Car
Satisfied Customers: 21717
Experience:  Automotive Engineer for 20 years, BEng hons degree,
Type Your Australia Car Question Here...
Matt is online now
A new question is answered every 9 seconds

Have a 2005 renault megane 2.0L VVT, has ~180k kms on the

Customer Question

have a 2005 renault megane 2.0L VVT, has ~180k kms on the clock and is running terribly. The car surges and hesitates as if it's not getting enough fuel, will sometimes run after full open throttle but usually returns on overrun. I have noticed the fuel pump seems to stop at this time as though it isn't getting power, I've had the dephaser pulley and solenoid changed, crank angle sensor changed and some minor wiring harness damage mended due to a substandard engine swap, as well as 4 new coils and even had an auto electrician look at the fuel pump plug. The pump itself has also been changed and I'm starting to run out of options. Further scans seem to point to the dephaser but that's been inspected since replacement and deemed okay.
I don't really want to get rid of the car as there's not much out there that strikes my fancy at the moment
Submitted: 1 year ago.
Category: Australia Car
Expert:  Matt replied 1 year ago.


This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattenedpiece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or bad pump power supply will all result in insufficient fuel being delivered to the engine

Expert:  Matt replied 1 year ago.


do you still need help?

Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you

Customer: replied 1 year ago.
Hi, thanks for the advice. I haven't forgotten to rate I've just not yet managed to have a look at the car but I intend to soon. I've moved it about a few times though and it seems to only come up after its been revved a little. Starts smooth and idles fine but after the cars moved or revved for a minute or two it happens. I will keep you posted as to the results.
Expert:  Matt replied 1 year ago.


good luck